<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
    
</head>
<body>
    <script>
       function demo(){
        console.log("demo...");
        return '666';
        //如果没有ruture,则返回undefined
       }

       var a = demo(); //函数调用
       var b = demo;   //函数引用

       console.log('a:'+a);
       console.log('b:'+b);
       console.log(b());

    </script>
    
</body>
</html>